[TF-M] Removal of the nRF5340 PDK platform

Hello,

As announced on March 3 (see https://lists.trustedfirmware.org/pipermail/tf-m/2021-March/001516.html) and in the absence of objections, the nRF5340 PDK platform (nordic_nrf/nrf5340pdk_nrf5340_cpuapp) has been deprecated in the v1.3.0 release and the release is the last one to support this platform. Today, the code and documentation related to this platform have been removed from TF-M.

Best regards, Andrzej Głąbek